Appendix E Falcon Lead Lag
E-15
Modulation sensor (steam) - choices are S1 (J8-4) and S2 (J8-6). Default is S2, the system header
pressure transmitter. In the event of a header pressure transmitter failure, the local transmitter (S1)
can be configured as the lead lag modulation sensor.
Note that in steam systems the modulation backup source must be manually configured. In hydronic
systems this selection will be made automatically based on the settings in Modulation backup
sensor above.
On, Off hysteresis - The LL hysteresis values apply to all setpoint sources. The behavior of the
hysteresis function is identical to the behavior of the stand-alone hysteresis function, except:
• Where stand-alone hysteresis uses the on/off status of a single boiler, the LL hysteresis
uses the on/off status of all slave boilers: this status is true if any slave boiler is on, and
false only if all are off.
• Where stand-alone hysteresis uses time of turn-on and turn-off of a single boiler, the LL
hysteresis uses the turn-on of the first slave boiler and the turn-off of the last slave boiler.
PID gain - The behavior of the lead lag PID function is identical to the behavior of the stand-alone
PID function. The same gain scalers and algorithms are used.
Demand Switch - Selects the input for CH (steam) demand. If set to Disable, the LL master does
not respond to a demand.
Setpoint Source - Selectable between Local and S2 4-20mA for remote setpoint operation (hot
water only; see 6.4 above).
4mA/20mA Water Temperature (hot water only) - Defines the temperature range if S2 4-20mA
selected as setpoint source.
Outdoor Reset (hot water only) if enabled uses the current outdoor temperature to determine
setpoint (outdoor temperature sensor required; see 7.5 and 7.6 below).
Frost Protection (hot water only) is active when enabled and outdoor temperature is below the
Outdoor frost protection setpoint. If any slave indicates frost protection required, the Master will
turn on any pumps that are enabled for frost protection, and may additionally fire the current lead
burner at the Frost protection rate.
Lead lag selection method and rotation time together determine the sequence order of boilers.
Base load common - This is the firing rate threshold used for adding stages. If set to zero, this
parameter is disabled.
As demand increases, until all boilers are firing none will be requested to exceed the base load
common rate. Similarly, as demand decreases no boilers will be dropped until the load can be met
by remaining boilers firing at or below the base load rate.
The staging parameters (Add/Drop stage method, detection time, and interstage delay; error
threshold, rate offset) together determine, based on demand, when a boiler in the sequence will be
requested to turn on or off.
7.2 - Lead Lag Slave Configuration
It wi
ll be convenient to rema
in at the Master host boiler to configure the unit as a Slave (recall that
the lead lag Master is a communication function and not a separate controller - the Falcon hosting
the Master must also be configured as a Slave in order to be available to the lead lag network).
1. Go to CONFIGURE>Lead Lag Slave Configuration.
2. Available parameters are shown in Table 3. Make any necessary changes at this time.
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